Comparison of PLC, Soft-PLC, and Modern Control Solutions

Introduction

Industrial automation constitutes the foundation of contemporary production methodologies. It enhances efficiency, diminishes expenses, and facilitates accurate operation of intricate machinery. Historically, programmable logic controllers (PLCs) have been employed for this function, demonstrating their value through durability and real-time performance. As digitalisation and Industry 4.0 progress, new demands for flexibility, connectivity, and scalability emerge.

Traditional PLCs predominantly adhere to the IEC 61131 standard, however Soft-PLCs provide a software-centric alternative that operates independently of proprietary hardware. IEC 61499 advances an event-driven and distributed automation paradigm. Simultaneously, advanced programming languages such as C++ and Rust are increasingly being utilised for the development of more robust and modular control logic.

What are the practical differences between these approaches? When is one option more suitable than the other? How can contemporary programming languages be integrated with established automation standards and platforms such as Xentara? This article offers a summary of these technologies and their potential to complement or substitute one another.

Classic PLCs – Structure and Function

Hardware-Based Controllers

Conventional PLCs are independent industrial control systems using custom-engineered hardware. They generally comprise a CPU, input/output modules, and communication interfaces. These systems are engineered for uninterrupted functionality in demanding industrial settings, providing exceptional reliability and real-time performance.

IEC 61131 as an Established Standard

The IEC 61131 standard delineates programming languages for traditional PLC systems, encompassing Instruction List (IL), Structured Text (ST), and Function Block Diagram (FBD). It has evolved into an internationally acknowledged standard, facilitating interoperability across many vendors' control systems.

✅ Advantages:

• High stability and real-time capability
• Long service life and industrial-grade robustness
• Standardized programming via IEC 61131
• Widely adopted and proven in industry

❌ Disadvantages:

• Limited flexibility and scalability
• Proprietary hardware dependence
• Limited support for modern software technologies
• Higher cost compared to software-based solutions

Soft-PLCs – The Software-Based Alternative

Definition and Differences to Classic PLCs

A Soft-PLC is a software-based equivalent of a conventional PLC that operates on regular industrial PCs or embedded systems. In contrast to hardware PLCs, Soft-PLCs are not constrained to particular hardware and can operate freely across several platforms.

IEC 61131 in Soft-PLCs

Despite operating independently of proprietary hardware, many Soft-PLCs continue to adhere to the IEC 61131 standard. This enables the reutilization of existing PLC programs while leveraging contemporary IT infrastructure.

✅ Advantages:

• High flexibility and scalability
• Cost savings through the use of standard hardware
• Easy integration with IT and cloud systems
• Independence from proprietary control hardware

❌ Disadvantages:

• Lower real-time performance compared to classic PLCs
• Dependency on operating system and hardware
• Increased cybersecurity and stability requirements

IEC 61499 – The Distributed Automation Approach

Core Principles of the IEC 61499 Standard

IEC 61499 was created to facilitate adaptable and scalable automation appropriate for dispersed systems and contemporary industrial applications. It delineates a event-driven architecture, wherein function blocks (FBs) are activated by events instead of being run in predetermined cycles. This enables systems to react more adaptively and effectively to environmental alterations.

Event-Driven Instead of Cyclic Processing

In contrast to traditional PLC systems that function on a cyclic loop, IEC 61499 relies on event-driven processing. Function blocks are executed solely in response to pertinent events. This results in enhanced resource utilisation and expedited response times.

Comparison to IEC 61131 and Relevance for Modern Connected Systems

IEC 61131 was developed for cyclic and hardware-constrained systems, whereas IEC 61499 addresses the requirements of contemporary, networked systems. It facilitates distributed execution, allowing functionality to be allocated among several devices and machines inside a network. In the context of Industry 4.0, this facilitates more adaptable and effective communication among equipment, particularly advantageous in intricate, dynamic contexts.

✅ Advantages:

• Event-driven processing allows efficient resource use and quicker responses
• Distributed architecture ensures flexibility and scalability
• Modular design simplifies maintenance and extension
• Seamless integration into networked systems and Industry 4.0

❌ Disadvantages:

• Higher development effort due to more complex programming
• Lower real-time capability than classic PLCs
• Less widespread and supported compared to IEC 61131

High-Level Languages like C++ or Rust for Control Systems

Why Use High-Level Languages?

C++ and Rust offer enhanced flexibility and performance in automation, facilitating precise management of intricate logic and seamless interface with contemporary IT infrastructures.

Advantages over Classic PLC Languages

High-level languages provide precise control of system resources and endorse object-oriented programming, enhancing maintainability and modularity.

Real-Time Capability, Memory Management, and Performance

C++ and Rust provide meticulous control over real-time performance, memory management, and efficiency, which is advantageous in resource-demanding applications or when utilising specialised hardware.

Security Aspects (e.g., Rust for Safe Memory Management)

Rust is very appropriate for safety-critical applications. Its architecture mitigates memory leaks and buffer overflows by rigorous memory management, leading to enhanced stability and security.

✅ Advantages:

• High flexibility and performance for complex applications
• Detailed control over memory and execution
• Safer programming through Rust’s memory safety model
• Easy integration with modern IT tools and systems

❌ Disadvantages:

• Higher development complexity compared to PLC languages
• Requires in-depth knowledge of real-time OS and automation principles
• Integration with existing automation systems can be complex
• Real-time capability may vary depending on implementation

Xentara as an Integration Platform for Modern Automation

Compatibility with Classic PLCs

Xentara facilitates integration with conventional PLCs adhering to the IEC 61131 standard, allowing for uninterrupted communication within established automation systems. This facilitates the integration of legacy PLCs into contemporary designs without necessitating hardware replacement or alteration of current logic. Xentara's adaptability enables various automation devices to interact and function on a unified platform.

Example interfaces: Beckhoff ADS, Siemens Put/GET, Ethernet/IP, Profinet, PLC vendors, etc.

Support for Soft-PLCs

Xentara additionally accommodates Soft-PLCs operating on industrial PCs or embedded systems, providing enhanced flexibility and scalability. These Soft-PLCs can be included into a cohesive control system with Xentara.

Examples: CODESYS, Beckhoff TwinCAT, Siemens SIMATIC, etc.

Event-Driven Control with IEC 61499

Xentara endorses the distributed, event-driven automation framework of IEC 61499. It facilitates communication and collaboration across function blocks across devices inside a network, hence enhancing efficiency in networked production systems.

Examples: 4DIAC, CODESYS

Control Using High-Level Languages Like C++ or Rust

Xentara permits the utilisation of C++ and Rust for the development of control logic. This facilitates the development of high-performance, secure applications designed for contemporary automation requirements. Xentara streamlines the incorporation of these apps into the comprehensive automation platform.

Example: Xentara CPP Skill

Advanced Features: Integration with IT and ML (AI) Applications

Xentara's distinguishing characteristic is its capacity to integrate control logic with IT systems and AI/ML applications. This facilitates predictive maintenance, issue identification, and process optimisation through real-time processing of live data from machines, sensors, and systems.

Example interfaces: ONNX, Pytorch, Tensorflow Lite, MQTT, OPC UA, REST, Websocket, etc.

Benefits of Xentara for Modern Automation Architectures

Xentara serves as a central integration platform, linking various control systems and technologies. It facilitates the modernisation of current systems by incorporating Soft-PLCs, advanced programming languages, and artificial intelligence capabilities. Xentara facilitates seamless communication across all components, enabling firms to construct efficient, future-proof automation systems. Its endorsement of AI and ML facilitates proactive, data-informed optimisation and decision-making.

Conclusion

Industrial automation is advancing, and conventional PLCs are encountering limitations regarding flexibility, connectivity, and scalability. Soft-PLCs and IEC 61499 provide contemporary alternatives that provide flexible, resource-efficient automation. High-level languages like as C++ and Rust provide enhanced capabilities and safety, particularly for intricate or safety-sensitive applications.

Xentara is a pivotal enabling technology that facilitates the integration of contemporary methodologies, allowing smooth connectivity among PLCs, Soft-PLCs, high-level programming languages, and IT/AI applications. Its adaptability in accommodating both legacy and contemporary automation standards, along with event-driven processing and sophisticated data integration, renders it a future-ready platform for intelligent, adaptive, and predictive production.

Xentara enables enterprises to modernise and enhance their automation plans to address the challenges of Industry 4.0 through scalability, interoperability, and real-time capabilities.